INTERVENTIONS:

MEASUREMENTS AND MAIN RESULTS:

Mean gastric pH was higher in the ranitidine group (median 4.7, range 3.6 to 6.1) than in the control group (median 2.1, range 1.2 to 4.9; p less than .05). Gastric colonization occurred in 15 (94%) of 16 patients who received ranitidine, 2 days (median; range 1 to 5) after intubation; gastric colonization also occurred in all control patients (median 4 days, range 1 to 9; p less than .05). Pneumonia occurred in 13 (81%) of 16 patients who received ranitidine, 3 days (median, range 1 to 5) after intubation and in nine (50%) of 18 control patients (p less than .01) 5 days after tracheal intubation (median, range 3 to 14; p less than .01). Prior gastric colonization by the pathogen that caused pneumonia was demonstrable in nine (56%) of 16 patients who received ranitidine vs. eight (44%) of 18 control patients (p greater than .05). The risk for developing pneumonia in the ranitidine-treated group was highest in the first 4 days after tracheal intubation. There was no difference in the frequency of upper gastrointestinal hemorrhage in the two groups.